Thursday, October 9, 2008

MICRO SOLAR SYSTEM IN HAWAII

We designed a portable micro solar system to provide emergency backup electrical power if the local power system goes down. In Silicon Valley we had a small Honda gas-powered generator used for emergency backup power for our computers and refrigerator. Power outages in the Bay Area were common and we used the generator many times a year. Since we live in sunny Hawaii, instead of the foggy Bay area, and the cost of gas and electricity is substantially higher here, we decided to make a portable micro solar system to use as our back up power supply and get the added benefit of reducing our electric bills by using it to generate power for everyday use like fans and other appliances.

About 15 years ago we had a small solar system at a mountain cabin in Colorado that was similar in scale to our design, with one solar panel and two batteries. We used it to power compact florescent bulbs for light at night and it did a fine job. Although the costs have remained about the same, our newly designed system has about 300% more battery storage and the electric controls are vastly better. Battery and solar panel technology have made a quantum leap in the last 15 years!

One of the challenges we ran into while cobbling together the system was finding all the parts and figuring out how to assemble them. After collecting parts for over 6 months, we wondered if wiring them together would cause the batteries to explode or get us electrocuted in the process. We convinced our favorite brilliant mechanic friend to come over and show us how to hook the system up without getting killed and thanks to him, the system is now up and running.

We strongly advise that you do not assemble a solar system without help from a licensed electrician. The improvements in batteries and solar panels mean there is much more electrical power in the system and a corresponding higher risk for injury.

The Micro Solar System

Here are the components of the system, their cost, and where we bought them.

At Hilo Propane and Gas we bought a Mitsubishi solar panel for $792;

a Morningstar Prostar-50 Solar Charge Controller for $260;

and two Trojan T-650 deep cycle 6 Volt batteries and a Series cable for $300.

The batteries are sitting on a water hose cart we bought for $65 at Home Depot in Hilo. Home Depot cut plywood to size for the batteries to sit on for $9.

The blue wire was also purchased there for $23.

At Solar Works in Ocean View we bought a Coleman 800 Watt Power Inverter for $135.

At Ace Hardware in Hilo we bought plastic wire connectors for $5.

It isn’t pretty, but the system works and the cost for everything was about $1500 including the cart to make the heavy batteries transportable.

Here is a wiring chart of the experimental system.

In this design, we have not solved how to ground the solar panel or power inverter (in case of a lighting strike). Grounds typically involve pounding a long copper rod into the ground to hook the grounding wire. That implementation would defeat the portability of the system and since we are on solid lava rock, it is not possible to pound a rod into the ground. The solar panel is large and heavy to move in and out each day and though the batteries are on a cart, they are so heavy it is difficult to push. And the connectors to the controller are difficult to work with as the solar power wire is spun so that it is a challenge to attach it to the controller.

We are interested in making improvements to the system like utilizing new battery types that are lighter making the system more portable. There are new types of solar panels available that are adaptable in size and shape. We are eager to hear about portable solar systems that others are working on.

11 comments:

Congratulations on your solar installation. It illustrates what can be done with some ingenuity and persistence. My company, Solar Stik(www.solarstik.com) , produces a high-end ready made solution that has some advantages over your system (although it does cost more). Solar Stik adjusts manually to point at the sun directly, getting 300 Watts of power out of 100 Watts of solar panels. Because our panels our elevated, they stay cooler and therefore perform better. Lastly, we use the best marine deep cycle batteries for the best power storage you can find. Our current product line is aimed at government and institutional users, but we are coming out with a less expensive consumer version next year. So keep checking our website! Thanks for the opportunity to comment. Al Zaccor, CEO, Solar Stik.

Your setup looks small, but as I understand it is efficient enough. Your suggestion is correct. Without any expert guide, one must not attempt to make this thing. I would recommend one to buy one instead to be on the safer side.